Problem

User notification, "System Disconnected or Junction Disconnected because of element <element label name>", when computing a model.

Problem ID#: 58910

Solution

At the time step when this user notification occurs the system is disconnected because of the element listed. This means that the hydraulic grade cannot be determined in the disconnected elements because they are not connected to a boundary condition.

This can happen in a number of different situations where the element is hydraulically disconnected from a source, such as:

1) If an upstream tank becomes full or empty and the built-in altitude valve shuts the adjacent pipe. To check for this, graph percent full for the tank. A shortcut to do this for all elements is to click the Select By Element dropdown in the Home tab and choose Tank, then right click > Graph > Percent Full. You can also check your pump controls to make sure they're set up so that the tank never becomes full or empty. For further information on what happens when a wet well or tank becomes full or empty please refer to this article.

2) If a pump has been turned off by the controls or if the pump flow is zero at this time step and there is no other source (such as a tank) to supply downstream demands.

3) If elements between the element in question and a source are set to inactive. If a node at the end of a pipe is inactive, but the pipe is active, you may see a user notification like this.

4) If a PRV, PSV or FCV are closing dynamically based on the hydraulic conditions. For example if a PRV is placed just before a hydrant and the hydrant has no demand, it cannot throttle to maintain the desired pressure (without any flow), so it will be set to Closed, and hence the hydrant will be disconnected.

5) If a check valve or pipe is set to closed, cutting off the elements in question from a source. Try color coding on the calculated "Is closed?" status, using "color and size", with a larger size for those with "Is Closed?" set to True. Then, zoom out and look for thicker pipes with the color you chose (such as red).

See Also

Disconnected Demand Nodes user notification when computing model 

User notification for nodes disconnected from an outfall, however all nodes appear to be connected